Hydraulic pump



Sept. 14, 1965 R. DAUB 3,205,832

HYDRAULIC PUMP Filed Aug. 28, 1962 3 Sheets-Sheet 1 INVENTOR Sept. 14, 1965 R. DAUB 3,205,832

HYDRAULIC PUMP Filed Aug. 28, 1962 s sheets-sheet 2 INVENTOR BY Ruda/ph 00L/b R. DAUB HYDRAULIC PUMP Sept. 14, 1965 3 Sheets-Sheet 3 Filed Aug 28' 1962 INVENToR Ruda/ph 00L/b United States Patent 3,205,832 HYDRAULIC PUMP Rudolph Daub, 9 Hickory Drive, Box 106, North Caldwell, NJ. Filed Aug. 28, 1962, Ser. No. 219,987 6 Claims. (Cl. 103-173) This invention relates to axial type pumps having a cylinder block axially movable to vary the fluid displacement.

In pumps of this type the pump pistons have a constant stroke. The capacity or fluid displacement of the pump s varied by axially moving the cylinder block to vary the effective stroke of the pistons. The cylinder block is usually held in the maximum displacement position by a helical spring and is moved to a lesser displacement by hydraulic pressure applied against the cylinder block in opposition to the spring pressure. The displaced fluid is discharged from the pump through a stationary valve housing coupled to the cylinder block by fluid transfer means.

An object of this invention is to provide an axial type of hydraulic pump that has a cylinder block sensitively adjustable for varying the capacity of the pump by having fluid transfer means between the cylinder block and valve housing without imposing side loads on the bores of the cylinder block.

Another object of this invention is to provide an axial type hydraulic pump that has fewer parts and is less expensive than present comparable pumps and has a greater versatility in adjustment.

Another object of this invention is to provide an axial type hydraulic pump with a movable cylinder block that has damping means impeding the movement of the cylinder block.

A further object of this invention is to provide sealing means between the cylinder block compartment and the wobble plate compartment of an axial type hydraulic pump.

Other and further objects and advantages will be apparent from the following description.Q taken in connection with the drawings, in which FIGS. l and 2 are separate fragmentary sectional views of the pump taken through the main axis;

FIG. 3 is a fragmentary sectional view of the bore of the cylinder to illustrate a reduced effective stroke;

FIG. 4 is a fragmentary view of the valve housing illustrating the pressure adjusting valve in a position to provide pressure to alter the position of the cylinder block;

FIG. 5 is a sectional view of the valve housing taken along lines V-V of FIG. l;

FIG. 6 is a fragmentary view of the wobble plate housing illustrating the yoke holding the wobble plate from rotation taken along lines VI-VI of FIG. 2;

FIG. 7 illustrates a modification of the cylinder block with means for supplying fluid to the bore on the retraction of the pump piston; and

FIG. 8 is another embodiment of the resilient sleeve sealing the valve housing compartment from the wobble plate housing compartments.

Referring to the drawings, the cylinder block 10 is slidably mounted on a center positioned projection 11 formed as part of a partition member 12 extending transverse 'to the main axis A of the pump and has longitudinally extending bores 19 with pump pistons 13 at one end and valve pistons 14 at the other end. The valve pistons are actuated by a wobble plate 15 by means of push rods 16. The valve pistons 14 are part of the fluid transfer means coupling the cylinder block 10 and the valve housing 17 for delivery of fluid under pressure to the valve housing and discharge at the outlet 18.

The cylinder block 10 is forced by the spring 20 to a full effective stroke position. This force is countered by fluid pressure applied to the chamber 21 between the projection 11 and the cylinder block 10. On increase in pressure in the chamber, the spring is compressed and the cylinder block moved toward the valve housing and the effective stroke reduced. The cylinder block has a plurality of longitudinally extending bores 19 with the pump pistons 13 and the valve pistons 14 fitting snugly therein to prevent oil leakage therearound and to support the pistons in the block. The pump pistons 13 reciprocate in relation to the axially ported valve pistons 14. Ports 25 and 26 are intermediately positioned to supply fluid to the bores from the fluid supply compartment 27 formed by the valve housing 17 and the partition member 12. A fluid supply connection 22 is provided through the housing 17.

In FIG. l the cylinder block is at the full effective stroke position, so that the pistons 13 cover the ports 25 and 26 in the initial portion of the stroke to provide the maximum amount of fluid between the pump piston and the valve piston. As the cylinder block 10 is moved towards the valve housing, the ports 25 and 26 are moved closer to the valve pistons delaying the cutoff of the ports, thereby reducing the effective stroke of the piston.

ln the modification of FIG. 7 the cylinder block 10 has ducts 58 adjacent to the faces of the valve pistons for supplying fluid to the bore 19 through check valves 59 on the return stroke of the respective pump piston. This supply of fluid permits the ports to have a lesser port height H than the ports of the embodiment of FIG. 1. This provides a longer effective stroke and increases the volumetric efficiency.

The valve pistons 14 are coupled to the check valve block 28 by the hollow swivel joints 29 havin-g passages 30 receiving fluid from the orifice 57 in the valve piston. The swivel joints have rounded ends 31, 32 fitting in the `sloped seating surfaces or seats 88, 89 of the check valve block -and valve piston, respectively, to form fluidtight seals. The curvature on the swivel joint can vary from the respective curvatures on the pist-on or check valve to form thin circular high pressure seals. An initial pressure is provide-d by the helical springs 33 bearing against the valve housing and Valve pistons. The swivel joints 29 permit the valve pistons to accommodate to lateral movement of the cylinder block and also to compensate for tolerances between the bores and the valve seat. Side loads against the bores are eliminated while providing high pressure seals. The fluid is delivered past the check Valves 34 to the valve discharge chamber 36 extending circumferentially within the valve housing and thence to the discharge outlet 18.

Fluid pressure is supplied to the chamber 21 through passages 38 and 39 in the partition member and projection 11, respectively. The fluid pressure may be supplied to passage 38 either from the valve discharge chamber 36, through sleeve 52 or from a remote pressure control means (not shown) through the socket 37.

The fluid pressure from the chamber 36 is controlled by the Valve 40 which has a stern slideably fitting in the bore 41 and a lateral head 42 in the chamber recess 43. A helical `spring 44 bears against the lateral head 42 at one end and against the Ispring retainer 45 at the other. The spring retainer is adjustably held by the pressure adjustment screw 46 threaded in the end cover 17a and rotatably bearing against the retainer. Thus the pressure applied 'by the spring to the valve may be adjusted. Fluid pressure is applied to the opposite end of the valve by the passages 47 and 48 connecting the chamber 36 to the bore 41. As the pressure increases in the chamber 36 the valve is forced to the left to connect the pressure passage 49 to the passage 50 around the reduced portion 51 overlapping with the passage 50. The

ud pressure is applied through the passage 50 and the sleeve 52 connecting the valve housing and the partition member and thence to the passages 38 and 39. The adjustment of the spring length relates the movement of the cylinder block to the uid pressure developed. Vent passage 53 connects the passageSll around the reduced section to discharge fluid to the inlet pressure side of the pump and relieve the pressure in chamber 21 on the cylinder block assuming the full effective stroke position. Passage 75 connects the recess 43 with the supply compartment 27.

The remote pressure control means (not shown) is connected to the partition member 12 by means of the socket 37. The passage in sleeve 52 is blocked to prevent the application of fluid pressure from the chamber 36. The lluid pressure is then applied `by the remote control means through the passages 38, 39 to the chamber 21 for positioning the cylinder block.

In order to stabilize and dampen the cylinder block 10 an annular groove 60 is provided in the projection 11 to receive the steel ring 61 bearing against the cylinder block 10. Fluid pressure is supplied to the groove 60 by the duct 62 to force the ring against the cylinder block 10, thereby increasing the frictional relationship between the cylinder block and the projection 11.

Instead of the ring 61 two O-rings 99 may be provided around the projection 11 and axially spaced with a duct 100 extending from the passage 39 to apply pressure on the O-rings to dampen the movement of the cylinder block.

The cylinder block may 'be mechanically positioned by the rod 63 formed as part of the cylinder block and extending axially through the valve housing. A winged nut 64 is threaded on the rod and bears against the valve housing to compress the spring 20. A scale 65 is indexed by notch 66 to indicate the position of the cylinder block.

The pump pistons 13 extend through openings 80-in the partition member 12 and are driven by the wobble plate by means of the push rods 16. Ari initial and return force to hold the push rods against the wobble plate and the piston is provided by the helical springs 70 bearing against the partition member 12 and the end llange 71 of the pistons. The push rods have round ends 55, 56 to rotatably t in the seats in the pistons and wobble plate. The wobble plate 15 is eccentrically mounted to provide axial movement to each piston on a single rotation of the wobble plate. The cylinder block 10 is held against rotation by the intert of the key 67 and groove `68 in the valve housing.

The wobble plate is driven by and mounted on the wobble plate drive means 72 and is held against rotation by block 91 sliding in guides 90 in a conventional manner.

The wobble plate housing forms a chamber or compartment 74 for holding lubricating fluid and may be connected to the fluid supply chamber 27 by passages 76 if the hydraulic fluid can also serve as a lubricant. If the chambers are to contain diierent fluids, flexible sleeves 77 are positioned around the springs 70 and the pump pistons 13 and have flanges 78 seating against the partition member 12 and anges 79 seating against the flanges 71 on the pistons. The sleeves 77 seal the openings 80 through which the pistons 13 pass from the lcharnber 27 to the chamber 74.

The wobble plate drive means 72 comprises a stub shaft 81, eccentric member 82 and a d-riving flange member 83 mounted in the partition member 12 by needle bearing 84 and needle bearing 85 in housing 73. The ange member 83 is splined to the eccentric member 82 and secured thereto by bolt 86. A shaft seal 87 seals the compartment 74.

The check valves 34 slideably t in inserts 34a of the blocks 28 and have ats 93 in the stem to provide equalizing -lluid pressure at the back of the stems. Springs 94 press the valves against seats 95 to seal the block on e the return stroke. The check valve blocks are held in the valve housing by the cover 17a. The -springs 33 bear against piston llanges 97 and the valve housing flanges 98. The valve pistons are clear of the valve housing and form with the bores axially extending seals while the swivel joint ends provide spaced seals adjustable to the tilt of the joint. Thus the joints form sealed linkages between the valve pistons and the valve housing po-rts.

In FIG. 8 a modification of the means for sealing the openings l is illustrated. The springs 70 and sleeves 77 are replaced by spring bellows 101 seating on the partition member 12 and the llanges 71 of the pistons. Seals or gaskets 102 are placed at the ends of the bellows.

I claim:

1. An axial type hydraulic pump comprising an intermediate partition member extending normal to the axis of the pump and having a central axial projection, a cylinder block slideably supported by said projection, a valve housing mounted on said partition member on the same side as said projection and forming a iluid supply compartment containing said cylinder block, said cylinder block having longitudinally extending bores with reciprocating pump pistons and valve pistons, swivel joint means adjustably coupling said valve pistons and said valve housing for transference of Huid from said bores to said valve housings, said valve pistons and said valve housing having seats for receiving axial forces and said swivel joint means having rounded ends fitting in said seats to seal the transferred iluid by axial pressures of said valve pistons with minimal side loads on said cylinder block, said cylinder block and said projection forming a chamber toadjust the position ofssaid cylinder block under hydraulic pressure supplied to said chamber, and said partition member having passages for supplying fluid to said chamber to vary the position of said cylinder block with minimal frictional resistance with said valve pistons.

2. In an axial type hydraulic pump having an axially slideable cylinder block with bores having pistons driven by a drive means for supplying luid under pressure to a stationary valve housing and with a springV forcing said block to a full elective stroke position, a supporting center projection axially coincident with the pump axis and a cylindrical bore in said block having its axis coincident with the axis of the pump and `in sliding fitting relation with said projection to support said block with a sliding iit, said projection forming a chamber with said block and having means for supplying fluid under pressure to position said cylinder axially to vary the effective stroke of said pistons and having a resilient ring extending around said projection bearing against said. bore and having passage means connected to said supply means for providing fluid pressure against said ring to vary the friction between said slideable cylinder block and said stationary projection with the pressure.

3. In an axial type hydraulic pump having an axially movable cylinder block with axially extending bores having pistons driven by a drive means for supplying iluid under pressure to a stationary valve housing having lluid passing ports with seats therearound, a hydraulic fluid transmitting means between said stationary valve housing and said cylinder block for conveying hydraulic iluld from said bores to said valve housing, comprising valve pistons in said bores with fluid passing end ports having seatsv around said ports facing said housing seats and hollow iluid transmitting swivel joints having round surfaces at each end movably yiitting in said seats in said pistons and valve housings to form axial pressure tight seals with said pistons and housing for adjusting to lateral forces w1th minimal side loads between said pistons and said bores.

4. In an axial type hydraulic pump having an axially slideable cylinder block with bores having pistons driven by a drive means for supplying fluid under pressure to a stationary valve housing and with a spring forcing said block to a full effective stroke position, a supporting center projection axiallyvcoincident with the pump axis and a cylindrical bore in said block having its axis coincident with the axis of the pump and in sliding fitting relation with said projection to support said block with a sliding fit, said projection forming a chamber With said block and hav-ing means for supplying fluid under pressure to position said cylinder axially to vary the effective stroke of said pistons, resilient means bearing against said cylinder block and passage means connected to said supply means for providing fluid pressure against said resilient means to vary the friction between said slideable cylinder block and said stationary projection with the pressure.

5. An axial type hydraulic pump comprising an intermediate partition member extending normal to the axis of Ithe pump `and having a central axial projection, a cylinder block slideably supported by said projection, a valve housing mounted on said partition member on the same side as said projection -and forming a fluid supply compartment containing said cylinder block, said cylinder block having longitudinally extending bores with reciprocating pump pistons and valve pistons, swivel joint means adjustably coupling said valve pistons and said valve housing for transference of uid from said bores to said valve housing, said cylinder block and said projection forming a chamber, said partition and said projection having passages for supplying fluid under pressure to said chamber for adjusting the position of said cylinder block, and said projection having resilient means bearing against said cylinder block and means for supplying uid pressure to said resilient means to vary the frietional relationship between said slideable cylinder block and said projection.

6. An axial hydraulic pump comprising a partition member, a stationary housing forming a duid supply compartment with said partition member, said housing having valve blocks With ports for passing fluid and with sloped seating surfaces around each port facing said fluid supply compartment, a cylinder block in said compartment having longitudinally extending bores each with an intermediate intake port for supplying uid from said compartment to said bores and with reciprocable pump pistons and substantially stationary valve pistons containing passages for passing fluid, said partition member having a central axial projection extending into said compartment, said cylinder block slideably mounted on said projection and forming a closed chamber therewith and having resilient means urging said cylinder block toward said partition for full capacity operation, said projection having fluid supply passages for supplying duid under pressure to said chamber to gradually position said cylinder block for less than full capacity operation, said valve pistons having sloped seating surfaces facing the sloped seating surfaces of said valve blocks, joint means having passages for passing uids from said pistons to said blocks and rounded ends fitting in said sloped seating surfaces of said valve blocks and valve pistons forming `Huid-tight seals under the `axial pressure of said valve pistons to relieve the cylinder block of side loads, thereby permitting the cylinder block to respond to fluid pressures With minimal resistance from said valve pistons.

References Cited by the Examiner UNITED STATES PATENTS 2,106,592 1/38 Dick 74-18.2 X 2,250,608 7/41 Sherman 74-60 2,369,134 2/45 Cameron 103-4l.2 2,672,817 3/54 Friedlander 103-173 2,724,548 11/55 Bixler 230-206 2,990,781 7/61 Tuck et al. 103-37 2,996,240 8/ 61 Stocklein et al. 230-206 3,018,737 1/62 Cook et al 103-173 3,045,604 7/62 Hahn 103-173 3,099,218 7/63l Budzich 10S-37 FOREIGN PATENTS 527,690 10/ 40 Great Britain.

LAURENCE V. EFNER, Primary Examiner.

JOSEPH H. BRANSON, JR., ROBERT M. WALKER,

Examiners. 

1. AN AXIAL TYPE HYDRAULIC PUMP COMPRISING AN INTERMEDIATE PARTITION MEMBER EXTENDING NORMAL TO THE AXIS OF THE PUMP AND HAVING A CENTRAL AXIAL PROJECTION, A CYLINDER BLOCK SLIDEABLY SUPPORT BY SAID PROJECTION, A VALVE HOUSING MOUNTED ON SAID PARTITION MEMBER ON THE SAME SIDE AS SAID PROJECTION AND FORMING A FLUID SUPPLY COMPARTMENT CONTAINING SAID CYLINDER BLOCK, SAID CYLINDER BLOCK HAVING LONGITUDINALLY EXTENDING BORES WITH RECIPROCATING PUMP PISTONS AND VALVE PISTONS, SWIVEL JOINT MEANS ADJUSTABLY COUPLING SAID VALVE PISTONS AND SAID VALVE HOUSING FOR TRANSFERENCE OF FLUID FROM SAID BORES TO SAID VALVE HOUSINGS, SAID VALVE PISTONS AND SAID VALVE HOUSING HAVING SEATS FOR RECEIVING AXIAL FORCES AND SAID SWIVEL JOINT MEANS HAVING ROUNDED ENDS FITTING IN SAID SEATS TO SEAL THE TRANSFERRED FLUID BY AXIAL PRESSURES OF SAID VALVE PISTONS WITH MINIMAL SIDE LOADS ON SAID CYLINDER BLOCK, SAID CYLINDER BLOCK AND SAID PROJECTION FORMING A CHAMBER TO ADJUST THE POSITION OF SAID CYLINDER BLOCK UNDER HYDRAULIC PRESSURE SUPPLIED TO SAID CHAMBER, AND SAID PARTITION MEMBER HAVING PASSAGES FOR SUPPLYING FLUID TO SAID CHAMBER TO VARY THE POSITION OF SAID CYLINDER BLOCK WITH MINIMAL FRICTIONAL RESISTANCE WITH SAID VALVE PISTONS. 